Can an employer fire you because you have a disability?

My fianc�e is an EMT. He has been working at the same place for about 8 months. He has had a mild form of cerebral palsy all his life. It does not affect him to much, but it does makes him have to walk on the balls of his feet and it makes it hard to write. Recently, his boss told him since his reports were too sloppy she may have to fire him. I just wanted to know if she could do that legally? They could accommodate him with a computer to type the reports but they say it takes to much time. Can she really do this?